The painful protrusion of the sternal stalk bone may be due to several reasons: first, the presence of trauma related to this area. For example, a direct violent blow to the bone may cause soft tissue contusions or fractures in this area. Once these lesions occur, there will be significant swelling in the area, and bony deformities may occur, often accompanied by significant pain. Second, this condition may be caused by an infection in the area. For example, localized bacterial infection of some soft tissues on the surface or septic osteomyelitis inside the sternum may lead to significant swelling, bulging, and pain. Third, this condition may also be caused by prolonged compression here. For example, some patients have a protruding sternum due to congenital hereditary factors or acquired malnutrition, and if the patient takes a prolonged prone position and has prolonged compression on this part, it may cause a sterile inflammation here, which may lead to pain here.